The ever expanding amount of digital data provides an impetus for the continuing development of high capacity storage solutions. Technologies that are suitable for these applications include optical tape, magnetic tape, and optical disks. Of these possibilities, optical tape technology is believed to provide the greater storage capacity.
Optical storage devices utilize laser light to write and read data to an optically active storage disk that includes one or more optically sensitive layers onto which data is encoded. Such disks may or may not be rewritable depending on the specific compositions used on the disk and on the electro-mechanical design of the optical storage device. Examples of optical disks include compact disks (CD), DVDs, Ultra Density Optical disks, Blue Ray disks, and the like.
The typical optical tape medium includes a base film such as polyethylene naphthalate (PEN) over-coated with multiple layers for recording digital data. A polymeric imprint layer is usually disposed over the base film. In one type of optical tape, the imprint layer is over-coated with a reflective metallic layer that is, in turn, over-coated with a sequence of dielectric layer, phase change layer, and dielectric layer. The actual data recording and reading occurs in the phase change layer. In a typical application, a pulsed laser beam is projected from an optical head assembly onto the optical tape thereby causing a phase change in the phase change layer that results in data being encoded therein. Data encoded onto the optical tape is also read with a laser with the reflective layer reflecting light to a detector. Moreover, optical tape usually includes optical servo marks embossed into the imprint layer along the length of the tape for operating with a servo control system for controlling the optical head. Although the current optical tape technology works reasonably well, there are a number of problems related to the polymeric imprint layer.
Magnetic data storage is another common technology used to store digital information. In this technology, magnetic storage uses magnetic patterns which are encoded onto a magnetically coated surface to store data. Normally, data is encoded on magnetic media that is a thin web (i.e, a tape) that is wrapped inside of a cartridge. Magnetic heads are used to read/write data from the thin web. In a typical magnetic storage drive, the web is sent through a tape drive and a recording head that is typically magnetic in nature that gets close to the magnetic surface and records data on it. Typically, data storage disks have much higher storage density because the thin web tends to move in undesired directions. Therefore, registration is very important in the prior art magnetic storage designs.
Accordingly, the present invention provides improved methods and systems for storing digital data onto optical media with data transfer rates that approach that of optical storage disks.